The prior art in the field of the invention offers implantable drain valves for the treatment of glaucoma which typically comprise a main body which in turn is associated with a drainage tube, connected at one end to the main body.
The main body of the drain valve is implanted by the surgeon on the surface of the eye globe of the patient, in an area under the conjunctiva, while the drainage tube is implanted so as to penetrate with its tip inside the anterior chamber and therefore drain the aqueous humour therefrom.
More particularly the drainage tube has a first end which is connected to the main body of the drain valve and a second distal end, opposite the one connected to the main body, which is implanted by the surgeon, during the operation, so as to perforate with its tip the surface of the eye globe and therefore penetrate inside the respective anterior chamber.
In this way the drain valve, once implanted by the surgeon in the eye of the patient, allows, by means of the distal end of the drainage tube which penetrates the anterior chamber, the drainage of the aqueous humour from the inside to the outside of the eye globe where the aqueous humour is received by the main body of the valve, to then flow to the exterior of the same main body in an area below the conjunctiva.
The implant of this valve, with consequent drainage of the aqueous humour contained in the eye globe, is such as to reduce considerably the intraocular pressure so as to be effective in the treatment of glaucoma from which the patient is suffering.
In known drain valves the respective drainage tube, which is implanted in the eye of the patient so as to penetrate the interior of the eye globe, and in particular the portion, of the drainage tube, which is connected and adjacent to the main body of the valve and is therefore placed, in the surgical operation, over the external surface of the eye globe, usually has a circular section.
Now this particular circular shape in section of the drainage tube is such as to generate an encumbrance, on the ocular surface, which in turn is found to be the cause of discomfort for the patient in whom the valve has been implanted, given that this encumbrance hinders the movement of the eyelids which have to close and open often to lubricate the ocular surface.
For completeness of information, FIG. 8 of the drawings shows a drain valve, of the conventional type and complying with the prior art, which has a drainage tube exhibiting such a circular section.
These however are not the only disadvantages, limits and defects of the drain valves known and currently used in the medical field for the treatment of glaucoma.
In fact the drain valves currently available for the treatment of glaucoma do not appear such as to respond satisfactorily to some major needs and necessities which could arise and which the surgeon could have during the operation for implanting the drain valve.
For example known drain valves do not allow the surgeon to adapt, i.e. increase or decrease, the distance between the point wherein the drainage tube is implanted, and therefore penetrates the interior of the eye, and the valve itself, according to the specific circumstances and situations of the surgical operation to implant the valve in the eye of the patient.
Moreover a last but not least disadvantage, which can be found in known drain valves, is due to poor lubrication, in turn the potential cause of infections, which occurs in the zone of contact between the body of the drain valve and the outer surface of the eye globe whereon this body is implanted.
More particularly this considerable disadvantage occurs despite the fact that the main body of known drain valves is at times provided with several through holes which allow the placing in communication of the zone of the outer surface of the eye globe, on which the valve is placed and implanted, with the upper surface of the main body of the valve where the drained aqueous humour coming from inside the eye globe flows.
A further limit and disadvantage of known drain valves is connected to the fact that, in order to secure stably during the surgical operation the main body of the drain valve on the eye globe, the fixing holes, for the insertion of the yarn for fixing the main body of the valve on the outer surface of the eyeball, should be close, as far as possible, to the iris.
Instead, unfortunately, known drain valves have such a configuration as to involve a certain distance between these fixing holes and the iris, when it would instead be useful, for the reasons stated previously, i.e. to ensure more stable and robust attachment of the main body of the valve on the surface of the eye globe, for this distance to be smaller.
Among known drain valves intended for treatment of glaucoma and based on the principle of draining the aqueous humour contained in the anterior chamber so as to regulate the intraocular pressure, mention is made in particular of the so-called “Ahmed valve”.
In any case this type of valve, despite the fact it has had and continues to have wide application in the treatment of glaucoma, is also not to be considered free from disadvantages and limits recalled previously, so as to require further improvement.